A combined piston gas tightness detection device

Abstract

The application relates to the technical field of automobile part detection, and discloses a combined piston air tightness detection device, which comprises a rack, a lower pressing head, a liftable upper pressing head and a driving device; the bottom of the pressing seat of the upper pressing head is provided with an upper sealing gasket and forms an air channel in communication with a constant-pressure air source; the top of the lower pressing head is provided with a lower sealing gasket; during detection, the upper and lower sealing gaskets tightly adhere to the upper and lower surfaces of the piston to form a sealed test cavity; the constant-pressure air source fills the cavity with constant-pressure gas; the gas flow is detected in real time through a flow sensor, and compared with a preset threshold value, so that the piston sealing property is automatically determined; the application realizes full automation of the detection process, has high sensitivity and quantitative characteristics, overcomes the defects of low sensitivity, incapability of quantification and dependence on manual operation of the traditional bubble leak detection method, and significantly improves the detection efficiency, consistency and reliability.

Description

Technical Field

[0001] This invention relates to the field of automotive parts testing technology, and more specifically to a combined piston airtightness testing device. Background Technology

[0002] In the manufacturing process of automotive shock absorbers, after the powder metallurgy piston is manufactured, it needs to undergo a pressurized assembly process to form a combined piston. There may be microscopic gaps at the joint of this assembly. In order to ensure product reliability, a strict airtightness test must be performed on it before leaving the factory. At present, the industry usually uses a device based on water testing to perform this type of test.

[0003] In the prior art, such as the piston airtightness testing device disclosed in Chinese Patent Publication No. CN220437673U, its typical structure includes a base, a transmission device, and a sealing component. The base has a water storage tank and a through hole. During testing, the transmission device drives the sealing component (including the upper sealing component and the surrounding sealing components) to form a sealed cavity for the piston under test. Then, a pump is used to make gas flow through the piston. If there is a leak in the piston, the gas will pass through the leak point and enter the water in the water storage tank through the through hole. The airtightness is judged by observing whether ripples are generated on the water surface.

[0004] However, this detection method, which relies on visual observation of water surface ripples, has significant limitations. First, its detection sensitivity is significantly affected by the amount of leakage: when there are extremely small gaps at the joints of the combined piston, the leakage gas flow rate is low and the volume is small. The resulting bubbles or disturbances may not be enough to form clear ripples that are visible to the naked eye on the water surface, leading to missed detection and posing a potential risk to product quality control. Second, this method is a qualitative or semi-qualitative judgment, which can only roughly distinguish between "leakage" and "no leakage." It cannot accurately quantify and classify the degree of leakage, making it difficult to meet the needs of statistical analysis of leakage rates of different batches of products, process improvement, or higher-precision quality classification. Summary of the Invention

[0005] The technical problem that this application aims to solve is: how to provide a highly sensitive, quantitative, and automated method for detecting the air tightness of microscopic leaks at the press-fit joint surface of powder metallurgy composite pistons in automotive shock absorbers, so as to overcome the shortcomings of traditional bubble leak detection methods, such as insufficient sensitivity, inability to quantify judgment, and reliance on manual observation.

[0006] This invention provides the following technical solution: a combined piston airtightness testing device, comprising a frame, a lower pressure head disposed at the bottom of the frame, an upper pressure head located above the lower pressure head and movable vertically, and a drive device for controlling the lifting and lowering of the upper pressure head. The upper pressure head includes a pressure seat connected to the power end of the drive device. The bottom end of the pressure seat has a groove filled with an upper sealing gasket, and the pressure seat and the upper sealing gasket form an air passage for conveying airflow. This air passage is connected to a constant pressure gas source via a pneumatic conveying system and is equipped with a flow sensor for detecting gas flow rate. The lower pressure head includes a base mounted on the bottom wall of the frame. The top of the base has a groove filled with a lower sealing gasket. When the upper pressure head descends under the action of the driving device, so that the upper and lower sealing gaskets are in close contact with the upper and lower surfaces of the piston assembly to be tested, a sealed test chamber is formed around the piston assembly. At this time, a constant pressure gas source fills the sealed test chamber with gas at a constant pressure through the gas path. The equipment automatically detects the gas flow rate value through a flow sensor and determines the sealing performance of the product by comparing the flow rate value with a preset threshold.

[0007] Furthermore, a hollow opening is formed inside the combined piston; after the bottom end of the gas passage extends beyond the upper sealing gasket, its end position does not exceed the upper boundary of the hollow opening of the combined piston, so that when the upper and lower sealing gaskets are in close contact with the upper and lower surfaces of the combined piston, a sealed test cavity containing the hollow opening can be formed, ensuring that the detected gas flow originates only from any gaps that may exist at the piston assembly.

[0008] Furthermore, the pressure base includes an upper block, on which a mounting block and a lower block are detachably mounted at the top and bottom ends respectively; the upper pressure head also includes a docking pin located between the pressure base and the drive device; the mounting block is detachably connected to the power end of the drive device through the docking pin; a groove coaxial with the bottom center of the lower block is provided, and an upper sealing gasket is embedded in the groove.

[0009] Furthermore, a first air passage is formed within the upper module. One end of the first air passage extends through the side wall of the upper module for connection to the pneumatic conveying system, and a flow sensor is installed at this connection point. The other end extends towards the lower module and connects with a second air passage formed within the lower module. The bottom branch of the second air passage extends further to the location of the upper sealing gasket and aligns with a pre-set drainage channel inside the upper sealing gasket, thereby jointly constructing a complete air path.

[0010] Furthermore, the lower pressure head is coaxially provided with a positioning and cleaning assembly that can move vertically along its axial direction, and a linkage mechanism is provided between the power end of the drive device and the positioning and cleaning assembly; when the drive device runs and drives the pressure seat to rise and fall, its power end will synchronously drive the positioning and cleaning assembly to move along the axial direction of the lower pressure head through the linkage mechanism.

[0011] Furthermore, the positioning and cleaning assembly includes a cylindrical shell movably sleeved around the base and a positioning element arranged circumferentially inside the cylindrical shell; the positioning element can retract into the cylindrical shell due to contact with the side wall of the base, and when the cylindrical shell moves upward and causes the positioning element to disengage from the side wall of the base, the positioning element converges towards the center under the action of elasticity, thereby automatically centering and positioning the piston to be tested at the center of the lower sealing gasket.

[0012] Furthermore, the inner and outer sides of the cylindrical shell are respectively provided with an inner annular groove and an outer annular cavity, which are connected by a through pipe to form a path for the positioning member to move; the positioning member includes a gripper passing through the through pipe and a second spring located in the outer annular cavity and connected to the gripper; the end of the gripper near the combined piston is machined into a wedge-shaped structure.

[0013] Furthermore, the positioning and cleaning assembly also includes air guides fixed to the upper and lower sides of the cylinder shell, respectively. Each air guide is provided with an air inlet pipe and a distribution pipe from the outside to the inside, and the two are connected by a connecting pipe. An annular gap is left between the inner annular groove and the outer annular cavity, and the annular gap is connected to the distribution pipe. The inner sidewall of the annular gap is provided with a plurality of air grids arranged circumferentially and connected to the inner annular groove. The upper and lower air inlet pipes are connected to the air source through the same pipeline.

[0014] Furthermore, the positioning component also includes a gas distribution valve plate, one end of which is connected to the gripper, and the other end of which, after passing through the pre-set through grooves on the top and bottom walls of the outer annular cavity, bends horizontally inward and moves through the connecting pipe; the gas distribution valve plate is always confined within the connecting pipe and does not detach, and its surface is provided with an alignment opening for communicating with the connecting pipe.

[0015] Furthermore, the pneumatic conveying system includes a first pipe and a second pipe that are respectively connected to the air passage and the air inlet pipe. The first pipe and the second pipe extend outward and are connected together by a tee. The other end of the tee is connected to a constant pressure air source via a main pipe.

[0016] The technical effects and advantages of this invention are as follows: The combined piston airtightness testing device provided by this invention achieves the beneficial effects of high sensitivity, quantification, and automation. Specifically, through the coordinated operation of the upper pressure head, lower pressure head, pneumatic delivery system, and flow sensor, and utilizing the constant pressure gas source and flow detection principle, it can accurately measure the extremely small gas flow rate leaking through the microscopic gaps at the piston press-fit joint surface. Quantitative judgment can be made through a preset threshold, thus overcoming the inherent defects of traditional bubble leak detection methods, such as insufficient sensitivity, inability to quantify, and reliance on manual observation. The entire testing process, from forming a sealed test chamber by tightly pressing the upper and lower sealing gaskets against the piston, to constant pressure inflation, automatic flow rate detection by the flow sensor, and comparison with the threshold, requires no manual intervention, achieving fully automated operation and significantly improving testing efficiency, consistency, and reliability. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of Embodiment 1 of the present invention.

[0018] Figure 2 This is a front view schematic diagram of the cross-sectional structure of Embodiment 1 of the present invention.

[0019] Figure 3 For the present invention Figure 2 Schematic diagram of the structure at point A in the middle.

[0020] Figure 4 This is a schematic diagram of the first part of the airtightness testing method according to Embodiment 1 of the present invention.

[0021] Figure 5 This is a schematic diagram of the latter part of the airtightness testing method according to Embodiment 1 of the present invention.

[0022] Figure 6 This is a schematic diagram of the overall structure of Embodiment 2 of the present invention.

[0023] Figure 7 This is a cross-sectional structural diagram of Embodiment 2 of the present invention.

[0024] Figure 8 For the present invention Figure 7 A front view of the structure.

[0025] Figure 9 This is a schematic diagram of the frame, telescopic cylinder, docking pin, and linkage mechanism in Embodiment 2 of the present invention.

[0026] Figure 10 For the present invention Figure 9 The diagram shows the structure under different operating conditions.

[0027] Figure 11 This is a schematic diagram of the pressing head and positioning cleaning assembly in Embodiment 2 of the present invention.

[0028] Figure 12 For the present invention Figure 11 A schematic diagram of the shell and air guide section in the middle.

[0029] Figure 13 For the present invention Figure 12 Schematic diagram of the structure at point B.

[0030] Figure 14 For the present invention Figure 11 A schematic diagram of the cylindrical shell and positioning components.

[0031] Figure 15 For the present invention Figure 14 Schematic diagram of the structure at point C.

[0032] Figure 16 For the present invention Figure 14 The diagram shows the structure under different operating conditions.

[0033] Figure 17 For the present invention Figure 16 Schematic diagram of the structure at point D.

[0034] The attached figures are labeled as follows: 1. Frame; 2. Upper pressure head; 21. Pressure base; 211. Upper assembly; 2111. First air passage; 212. Lower assembly; 2121. Second air passage; 213. Mounting block; 22. Upper sealing gasket; 221. Drainage channel; 23. Connecting pin; 3. Lower pressure head; 31. Base; 32. Lower sealing gasket; 4. Telescopic cylinder; 5. Pneumatic conveying system; 51. First pipe; 52. Second pipe; 53. T-junction; 54. Main pipe; 6. Flow sensor; 7. Linkage mechanism; 71. Lifting part; 711. Pushing frame; 712. First guide rail; 713. Fixing frame; 714. Connector 72. Lug; 721. Retracting / releasing section; 721. Sliding plate; 7211. Guide groove; 722. Second guide rail; 73. Transmission section; 731. Push rod; 732. Third guide rail; 733. Guide sleeve; 74. First spring; 8. Positioning and cleaning assembly; 81. Cylinder shell; 811. Inner annular groove; 812. Outer annular cavity; 813. Through pipe; 814. Air grille; 82. Positioning component; 821. Gripper; 8211. Plug pipe; 8212. Contact; 8213. Plug plate; 822. Second spring; 823. Air distribution valve plate; 83. Air guide section; 831. Air inlet pipe; 832. Distribution pipe; 833. Connecting pipe. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. In addition, the forms of the various structures described in the following embodiments are merely illustrative. The combined piston airtightness detection device involved in the present invention is not limited to the structures described in the following embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1, refer to Figures 1 to 5As shown, the present invention provides a combined piston air tightness testing device, including a frame 1, a lower pressure head 3 disposed at the bottom of the frame 1, an upper pressure head 2 located above the lower pressure head 3 and movable vertically, and a drive device for controlling the lifting and lowering of the upper pressure head 2; the upper pressure head 2 includes a pressure seat 21 connected to the power end of the drive device, the bottom end of the pressure seat 21 is provided with a groove and filled with an upper sealing gasket 22, and an air passage for conveying airflow is formed in the pressure seat 21 and the upper sealing gasket 22, the air passage is connected to a constant pressure air source through a pneumatic conveying system 5, and is equipped with a flow sensor 6 for detecting gas flow rate; The lower pressure head 3 includes a base 31 mounted on the bottom wall of the frame 1. The top of the base 31 has a groove filled with a lower sealing gasket 32. When the upper pressure head 2 descends under the action of the driving device, so that the upper sealing gasket 22 and the lower sealing gasket 32 ​​are in close contact with the upper and lower surfaces of the piston assembly to be tested, a sealed test chamber is formed around the piston assembly. At this time, a constant pressure gas source fills the sealed test chamber with gas at a constant pressure through the gas path. The equipment automatically detects the gas flow rate value through the flow sensor 6 and determines the sealing performance of the product by comparing the flow rate value with a preset threshold. In this embodiment, it should be further explained that the combined piston specifically refers to a piston manufactured using powder metallurgy technology and composed of multiple metal parts joined together by high-pressure pressing in hydraulic systems such as automotive shock absorbers. Its core features are summarized as follows: Manufacturing and Structure: It is not processed from a single material, but rather the separately molded piston bodies are "cold-welded" together into an unremovable integral part by applying extremely high pressure in the axial direction using the interference fit principle to cause slight plastic deformation. Purpose and advantages: This design aims to meet the stringent requirements of pistons for high strength, complex internal oil passages, and multi-functional integration; the combination of near-net-shape finishing capabilities and pressurized assembly processes is the key to achieving high-performance, low-cost manufacturing of this complex structure. Key challenge: This process has an inherent risk – microscopic gaps invisible to the naked eye may form at the press-fit joint surface; these gaps can become leakage channels for the working oil, leading to damping failure, performance degradation, and abnormal noise in the shock absorber. Testing requirements: The core object of the airtightness test of the "combined piston" is the "metal-to-metal press-fit joint surface"; Therefore, a hollow opening is formed inside the combined piston; after the bottom end of the gas path extends out of the upper sealing gasket 22, its end position does not exceed the upper boundary of the hollow opening of the combined piston, so that when the upper sealing gasket 22 and the lower sealing gasket 32 ​​are in close contact with the upper and lower surfaces of the combined piston, a sealed test chamber containing the hollow opening can be formed, ensuring that the detected gas flow originates only from the gap that may exist at the piston assembly, effectively avoiding other leakage misjudgments caused by improper gas path outlet position or connection with other non-test parts that are not defects in the combined piston assembly itself; Among them, the airtightness testing method is: S1, Detection begins; S2. Place the piston assembly to be tested on the lower sealing gasket 32; S3. The drive device controls the pressure seat 21 to move the upper sealing gasket 22 towards the base 31 and press it down until the upper sealing gasket 22 and the lower sealing gasket 32 ​​are tightly pressed against the upper and lower surfaces of the combined piston. S4. By using the pressure sensing system or displacement sensing system installed in the pressure seat 21 and the base 31, determine whether the contact surfaces of the upper sealing gasket 22, the lower sealing gasket 32 ​​and the combined piston have reached a tight fit; if so, a sealed test chamber is formed around the piston assembly; if not, the alarm system is triggered and the adjustment is returned. S5. The constant pressure gas source fills the sealed test chamber with gas at a constant pressure through the gas passage constructed inside the pressure seat 21 and the upper sealing gasket 22. S6. When the pressure inside the cavity stabilizes at the preset value, the gas flow rate is automatically detected by the flow sensor 6, and the real-time flow rate is compared with the preset flow rate threshold. If the real-time flow rate is greater than or equal to the threshold, the product is determined to be "unqualified", that is, there is a leak at the assembly. The control system outputs an "unqualified" signal and links the subsequent actuators to perform audible and visual alarms, marking, or sorting operations. If the real-time flow rate is less than the threshold, the product is determined to be "qualified", that is, the assembly is well sealed. The control system outputs a "qualified" signal and links the subsequent actuators to light up a green light or guide the workpiece to the next station. S7. This testing process is now complete. To achieve diverse combinations of air passages in the upper pressure head 2 and facilitate maintenance, further adjustments are needed to the structure of the pressure base 21 and the upper sealing gasket 22. Specifically, the pressure base 21 includes an upper assembly 211, with a mounting block 213 and a lower assembly 212 detachably mounted at its top and bottom ends, respectively. The upper pressure head 2 also includes a docking pin 23 located between the pressure base 21 and the drive device. The mounting block 213 is detachably connected to the power end of the drive device via the docking pin 23. The lower assembly 212 has a groove coaxial with it at its bottom center, and the upper sealing gasket 22 is embedded in the groove. The top of the upper block 211 is embedded in the mounting block 213, and coaxial pin holes are opened at corresponding positions of the two, and they are fixed by horizontally arranged pins or bolts; the contact surfaces of the upper block 211 and the lower block 212 are kept in horizontal contact, and coaxial pin holes that can avoid the internal air passage are opened on the corresponding surfaces of the two, and they are fixed by vertically arranged pins or bolts. The driving device is a telescopic cylinder 4, which includes, but is not limited to, a hydraulic cylinder, a pneumatic cylinder, or an electric cylinder; in this embodiment, a hydraulic cylinder is preferred. An L-shaped first air passage 2111 is formed in the upper block 211. One end of the first air passage 2111 extends through the side wall of the upper block 211 and is used to connect with the pneumatic conveying system 5. A flow sensor 6 is installed at this connection. The other end extends in the direction of the lower block 212 and connects with a U-shaped second air passage 2121 formed in the lower block 212. The bottom branch of the second air passage 2121 extends further to the location of the upper sealing gasket 22 and aligns with the pre-set drain channel 221 inside the upper sealing gasket 22, thereby jointly constructing a complete air path. By splicing the upper block 211 or lower block 212 with different configurations, a variety of air paths can be constructed to meet different detection needs. The detachable splicing structure also facilitates the maintenance or repair of the internal air path.

[0037] Example 2 is based on Example 1. To further improve operational stability and achieve automated centering and positioning of the combined piston, and to avoid the inability to form an effective sealed test chamber due to misalignment of the combined piston, thereby preventing airtightness testing errors, further optimization of the equipment is required. The specific structure can be found in [reference needed]. Figures 6 to 12 , Figure 14 and Figure 16 As shown, the airtightness testing device also includes a positioning and cleaning assembly 8 that is coaxially arranged with the lower pressure head 3 and can move vertically along its axis. A linkage mechanism 7 is provided between the power end of the drive device and the positioning and cleaning assembly 8. When the drive device runs and drives the pressure seat 21 to rise and fall, its power end will synchronously drive the positioning and cleaning assembly 8 to move up and down along the axis of the lower pressure head 3 through the linkage mechanism 7. The positioning and cleaning assembly 8 includes a cylindrical shell 81 movably sleeved around the base 31 and a positioning member 82 arranged circumferentially inside the cylindrical shell 81; the positioning member 82 can retract into the cylindrical shell 81 due to the contact with the side wall of the base 31; when the cylindrical shell 81 moves upward and the positioning member 82 is disengaged from the side wall of the base 31, the positioning member 82 converges inward under the action of elastic force, thereby automatically centering and positioning the test combination piston at the center of the lower sealing gasket 32. The inner and outer sides of the cylindrical shell 81 are respectively provided with an inner annular groove 811 and an outer annular cavity 812, which are connected by a through pipe 813 to form a path for the positioning member 82 to move. The positioning member 82 includes a gripper 821 passing through the through pipe 813 and a second spring 822 located in the outer annular cavity 812 and connected to the gripper 821. The end of the gripper 821 near the combined piston is machined into a wedge shape. This design allows it to slide smoothly into or out of the side wall of the base 31 to achieve automatic extension and retraction, thereby stably completing the positioning and release action of the combined piston. The gripper 821 includes a plug tube 8211 that is movable through the through tube 813. One end of the plug tube 8211 is fixedly connected to a contact 8212 located in the inner annular groove 811, and the other end is fixedly connected to a plug piece 8213 located in the outer annular cavity 812, thereby restricting the movement of the gripper 821 to radial movement within this path; the bottom of the contact 8212 is machined into an inclined cross-section structure. The top sidewall of the base 31 is correspondingly machined into an inclined cross-section structure so that its interaction with the contact 8212 is smoother when it comes into contact with and bears pressure. In addition, a sliding structure can be further provided on the contact surface between the contact 8212 and the sidewall of the base 31, such as using a slide rail or adding a drag-reducing device, to effectively reduce the frictional resistance when the two move relative to each other. In use, when the cylindrical shell 81 is sleeved on the surface of the base 31 and has moved upwards but not yet detached, the contact 8212 in the gripper 821 abuts against the side wall of the base 31, causing the contact 8212 to be squeezed and retracted into the inner annular groove 811. At the same time, the plug 8213 compresses the second spring 822 to its limit position. As the positioning member 82 gradually detaches from the periphery of the base 31, the plug 8213 in the gripper 821 moves towards the center under the elastic restoring force of the second spring 822, driving the multiple grippers 821 arranged circumferentially to converge inwards synchronously, and finally through the contact... 8212 pushes the combined piston placed on the base 31 to the center of the lower sealing gasket 32; further, when the cylinder shell 81 moves down to reset, the contact 8212 will contact the side wall of the base 31 again, forcing the gripper 821 to be gradually pressed and retracted back into the cylinder shell 81, thereby removing the constraint on the combined piston and placing it in the center position of the lower sealing gasket 32, thereby realizing the automatic centering and positioning of the combined piston, effectively avoiding the inability to form an effective sealed test chamber due to its placement position deviation, and thus preventing the airtightness test error caused by this.

[0038] Example 3, based on Example 2, further optimizes the structure of the positioning and cleaning assembly 8 to improve the cleanliness of the combined piston and eliminate dust contamination interference before airtightness testing, thereby enhancing testing accuracy. The specific structure can be found in the following example. Figures 6 to 17As shown, the positioning cleaning assembly 8 also includes air guides 83 fixed to the upper and lower sides of the shell 81 respectively. Each air guide 83 is provided with an air inlet pipe 831 and a distribution pipe 832 from the outside to the inside, and the two are connected by a connecting pipe 833. An annular gap is left between the inner annular groove 811 and the outer annular cavity 812, and the annular gap is connected to the distribution pipe 832. The inner sidewall of the annular gap is provided with a plurality of air grids 814 arranged circumferentially and connected to the inner annular groove 811. The upper and lower air inlet pipes 831 are connected to the air source through the same pipeline, so that the clean airflow can flow through the air inlet pipe 831, the distribution pipe 832, and the annular gap in sequence, and finally be ejected from the air grids 814, acting on the surface of the combined piston and its surroundings. Furthermore, the positioning component 82 also includes a valve plate 823, one end of which is connected to the plug plate 8213 in the gripper 821, and the other end, after passing through the pre-set through grooves on the top and bottom walls of the outer annular cavity 812, bends horizontally inward and movably passes through the connecting pipe 833; the valve plate 823 is always confined within the connecting pipe 833 and does not detach, and its surface has an alignment opening for communicating with the connecting pipe 833; the valve plate 823 can move radially synchronously with the gripper 821, and when the contact 8212 pushes the combined piston and positions it at the center of the lower sealing gasket 32, The opening on the valve plate 823 is aligned and connected with the connecting pipe 833, allowing airflow to pass through and act on the periphery of the stabilized and constrained combined piston. This achieves coordinated operation of positioning and cleaning processes, effectively preventing the combined piston from shifting due to airflow impact during cleaning. In addition, the gripper 821 can be designed as a hollow structure, so that when the connecting pipe 833 is opened, the hollow interior can connect with the annular gap between the inner annular groove 811 and the outer annular cavity 812, thereby maximizing the airflow output area while ensuring its positioning function for the combined piston. Furthermore, the pneumatic conveying system 5 includes a first pipe 51 and a second pipe 52, which are respectively connected to the air path and the air inlet pipe 831. The first pipe 51 and the second pipe 52 extend outward and are connected together by a tee 53. The other end of the tee 53 is connected to the constant pressure air source via the main pipe 54. When the gripper 821 pushes the combined piston and positions it at the center of the lower sealing gasket 32, the opening on the air distribution valve plate 823 is accurately aligned and connected with the connecting pipe 833. At this time, the air source airflow can be diverted through the second pipe 52 to the connected air guide section 83, thereby acting on the periphery of the stably constrained combined piston for cleaning. When the gripper 821 releases the constraint on the combined piston, positions it at the center of the lower sealing gasket 32, and retracts to the side wall of the base 31, the air guide section 83 is closed. The airflow will only be supplied to the air path through the first pipe 51 to provide constant pressure airflow for subsequent air tightness testing. This system realizes the effective distribution and utilization of the same air source at different working stages. In use, when the gripper 821 pushes the combined piston and positions it at the center of the lower sealing gasket 32, the air distribution valve plate 823 moves radially synchronously with the gripper 821, so that the opening on the air distribution valve plate 823 is precisely aligned and connected with the connecting pipe 833, thereby forming a connected airflow channel between the air intake pipe 831, the distribution pipe 832, the annular gap, and the air grid 814; at this time, the air source airflow can be diverted through the second pipe 52 to the connected air guide section 83, and finally ejected by the air grid 814, acting on the periphery of the stably constrained combined piston for cleaning, realizing positioning and cleaning. The sequence is coordinated and linked; conversely, when the gripper 821 retracts to the side wall of the base 31 and releases the constraint on the combined piston, the gas distribution valve plate 823 moves with the gripper 821 so that its opening is misaligned with the connecting pipe 833, thereby blocking the airflow channel between the air guide 83 and the cylinder shell 81; at this time, the airflow is only supplied to the air path in the upper pressure head 2 through the first pipe 51; when the upper sealing gasket 22 and the lower sealing gasket 32 ​​are tightly attached to the upper and lower surfaces of the combined piston, a sealed test chamber is formed, and the constant pressure gas source fills the chamber with gas at a constant pressure through the air path for testing.

[0039] Example 4 is based on Example 2 or Example 3, with reference to... Figures 6 to 10 As shown, the linkage mechanism 7 includes a lifting part 71 connected to the docking pin 23, a retracting part 72 that can slide laterally along the left and right sides of the lifting part 71, a transmission part 73 disposed in front of each retracting part 72, and a first spring 74 that drives and connects the left and right retracting parts 72. When the power end of the drive device drives the lifting part 71 to move down through the docking pin 23, the lifting part 71 pushes the retracting parts 72 on both sides outward before the upper sealing gasket 22 contacts the combined piston, so that the transmission part 73 can drive the positioning and cleaning assembly 8 to move smoothly down along the surface of the base 31 under the guidance of the retracting part 72. This realizes that before the upper sealing gasket 22, the lower sealing gasket 32 ​​and the combined piston perform the alignment and sealing operation, the combined piston is automatically aligned and positioned and the surface is cleaned. In this embodiment, it is necessary to further explain that the lifting unit 71 includes a pusher frame 711 that is slidably connected to the front side of the first guide rail 712. The top end of the first guide rail 712 is fixed to the top end of the frame 1 by a fixing frame 713, and its bottom end is directly fixed to the bottom wall of the frame 1. The top end of the pusher frame 711 is fixedly connected to the docking pin 23 via a connecting lug 714, so that the pusher frame 711 can stably perform lifting and sliding along the first guide rail 712 under the drive of the docking pin 23. The bottom end of the pusher frame 711 is designed with a tapered structure to accurately open the sliding plates 721 on both sides to the required working position during the descent. To reduce movement resistance, pulleys are also provided along the outer contour sidewall of the pusher frame 711. The retracting section 72 includes a second guide rail 722 fixed to the bottom wall of the frame 1 and a sliding plate 721 slidably engaged thereon. A notch is reserved between the sliding plates 721 on the left and right sides for the conical structure at the bottom of the pusher 711 to enter. When the moving pusher 711 enters between the sliding plates 721 through the notch, its conical structure gradually expands the sliding plate 721 to both sides along the second guide rail 722. The two sliding plates 721 are connected by a first spring 74. When the pusher 711 rises and is withdrawn, the two sliding plates 721 can automatically return to the initial closed state under the elastic force of the first spring 74, thereby driving the transmission section 73 to complete the lifting transmission. The transmission unit 73 includes a third guide rail 732 fixed to the bottom wall of the frame 1 and a guide sleeve 733 slidably connected to the third guide rail 732. The guide sleeve 733 is fixedly connected to the cylindrical shell 81 and extends a push rod 731 from it in the vertical direction. The push rod 731 is slidably connected to the guide groove 7211 provided on the surface of the sliding plate 721. The guide groove 7211 is an inclined surface structure that slopes upward from the inside to the outside. When the sliding plate 721 slides to both sides under the action of the pusher 711, the push rod 731 is guided by the guide groove 7211 and drives the guide sleeve 733 and the positioning and cleaning assembly 8 fixed thereto to move downward as a whole. Conversely, when the sliding plate 721 converges inward under the elastic force of the first spring 74, the push rod 731 is guided by the guide groove 7211 and drives the guide sleeve 733 and the positioning and cleaning assembly 8 fixed thereto to move upward as a whole.

[0040] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, in accordance with the technical plan and its improved concept, should be included under the protection of the present invention.

Claims

1. A combined piston airtightness testing device, comprising a frame (1), a lower pressure head (3) disposed at the bottom of the frame (1), an upper pressure head (2) located above the lower pressure head (3) and movable vertically, and a drive device for controlling the lifting and lowering of the upper pressure head (2), characterized in that: The upper pressure head (2) includes a pressure base (21) connected to the power end of the drive device. The bottom end of the pressure base (21) has a groove and is filled with an upper sealing gasket (22). The pressure base (21) and the upper sealing gasket (22) form an air passage for conveying airflow. The air passage is connected to a constant pressure air source via a pneumatic conveying system (5) and is equipped with a flow sensor (6) for detecting gas flow. The lower pressure head (3) includes a base (31) installed on the bottom wall of the frame (1). The top end of the base (31) has a groove. The groove is filled with a lower sealing gasket (32); when the upper pressure head (2) descends under the action of the driving device, so that the upper sealing gasket (22) and the lower sealing gasket (32) are in close contact with the upper and lower surfaces of the piston assembly to be tested, a sealed test chamber can be formed around the piston assembly; at this time, the constant pressure gas source fills the sealed test chamber with gas at a constant pressure through the gas path, and the equipment automatically detects the gas flow value through the flow sensor (6) and determines the sealing performance of the product by comparing the flow value with the preset threshold.

2. The combined piston airtightness testing device according to claim 1, characterized in that: A hollow opening is formed inside the combined piston; after the bottom end of the gas passage extends out of the upper sealing gasket (22), its end position does not exceed the upper boundary of the hollow opening of the combined piston, so that when the upper sealing gasket (22) and the lower sealing gasket (32) are in close contact with the upper and lower surfaces of the combined piston, a sealed test cavity containing the hollow opening can be formed, so as to ensure that the detected gas flow originates only from the gaps that may exist at the piston assembly.

3. The combined piston airtightness testing device according to claim 1, characterized in that: The pressure seat (21) includes an upper block (211), on which an mounting block (213) and a lower block (212) are detachably mounted at the top and bottom ends respectively; the upper pressure head (2) also includes a docking pin (23) located between the pressure seat (21) and the drive device; the mounting block (213) is detachably connected to the power end of the drive device through the docking pin (23); a groove coaxial with the bottom center of the lower block (212) is provided, and an upper sealing gasket (22) is embedded in the groove.

4. The combined piston airtightness testing device according to claim 3, characterized in that: The upper block (211) has a first air passage (2111) inside. One end of the first air passage (2111) extends through the side wall of the upper block (211) and is used to connect with the pneumatic conveying system (5). A flow sensor (6) is installed at this connection. The other end extends in the direction of the lower block (212) and is connected to the second air passage (2121) inside the lower block (212). The bottom branch of the second air passage (2121) extends further to the location of the upper sealing gasket (22) and is aligned with the pre-set drain channel (221) inside the upper sealing gasket (22), thereby jointly constructing a complete air path.

5. The combined piston airtightness testing device according to claim 1 or 4, characterized in that: The lower pressure head (3) is coaxially provided with a positioning and cleaning assembly (8) that can move vertically along its axis. A linkage mechanism (7) is provided between the power end of the drive device and the positioning and cleaning assembly (8). When the drive device runs and drives the pressure seat (21) to rise and fall, its power end will synchronously drive the positioning and cleaning assembly (8) to move along the axis of the lower pressure head (3) through the linkage mechanism (7).

6. The combined piston airtightness testing device according to claim 5, characterized in that: The positioning and cleaning assembly (8) includes a cylindrical shell (81) movably sleeved around the base (31) and a positioning element (82) arranged circumferentially inside the cylindrical shell (81). The positioning element (82) can be retracted into the cylindrical shell (81) by the contact of the side wall of the base (31). When the cylindrical shell (81) moves upward and the positioning element (82) is disengaged from the side wall of the base (31), the positioning element (82) converges inward under the action of elasticity, thereby automatically centering and positioning the test combination piston at the center of the lower sealing gasket (32).

7. The combined piston airtightness testing device according to claim 6, characterized in that: The inner and outer sides of the cylindrical shell (81) are respectively provided with an inner annular groove (811) and an outer annular cavity (812), which are connected by a through pipe (813) to form a path for the positioning member (82) to move. The positioning member (82) includes a gripper (821) passing through the through pipe (813) and a second spring (822) located in the outer annular cavity (812) and connected to the gripper (821). The end of the gripper (821) near the combined piston is machined into a wedge shape.

8. The combined piston airtightness testing device according to claim 7, characterized in that: The positioning and cleaning assembly (8) also includes air guides (83) fixed to the upper and lower sides of the shell (81) respectively. Each air guide (83) is provided with an air inlet pipe (831) and a distribution pipe (832) from the outside to the inside. The two are connected by a connecting pipe (833). There is an annular gap between the inner annular groove (811) and the outer annular cavity (812). The annular gap is connected to the distribution pipe (832). The inner wall of the annular gap is provided with a plurality of air grids (814) arranged circumferentially and connected to the inner annular groove (811). The upper and lower air inlets (831) are connected to the air source through the same pipeline.

9. The combined piston airtightness testing device according to claim 8, characterized in that: The positioning component (82) also includes a gas distribution valve plate (823), one end of which is connected to the gripper (821), and the other end of which, after passing through the pre-set through grooves on the top and bottom walls of the outer annular cavity (812), bends horizontally inward and moves through the connecting pipe (833); the gas distribution valve plate (823) is always confined within the connecting pipe (833) and does not detach, and its surface is provided with an alignment opening for communicating with the connecting pipe (833).

10. The combined piston airtightness testing device according to claim 9, characterized in that: The pneumatic conveying system (5) includes a first pipe (51) and a second pipe (52) that are connected to the air passage and the air inlet pipe (831) respectively. The first pipe (51) and the second pipe (52) extend outward and are connected together by a tee (53). The other end of the tee (53) is connected to the constant pressure air source via the main pipe (54).

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